Apparatus for suspending a pipe within a well casing

ABSTRACT

Apparatus is disclosed for use in suspending a pipe from the lower end of a tubular body concentrically within an outer casing. Pockets are formed about the outer circumference of the body each to receive a cone having an inner conical side adjacent the inner wall of a pocket, and a slip having an inner conical side adjacent outer conical side of the cone.

[0001] This application claims the benefit of U.S. Provisional Application Serial No. 60/292,049 filed May 18, 2001, U.S. Provisional Application Serial No. 60/316,572 filed Aug. 31, 2001, and U.S. patent application Ser. No. 10/004,588 filed Dec. 4, 2001.

[0002] This invention relates generally to an apparatus for suspending a pipe within a well casing. More particularly, it relates to improvements in apparatus of this type in which the pipe is suspended within the casing by slips spaced equally about a body from which the pipe is suspended and adapted to be raised over a conical surface thereabout for expansion radially outwardly into gripping engagement with the casing, so that, the weight of the pipe may be slacked off onto the casing. The invention is of particular utility in suspending a liner hanger within an outer casing as disclosed in the aforementioned invention.

[0003] It is known that, in the design of a slip, a compromise must be made between slips of shallow taper and large taper—i.e., small or large angles between their cylindrical and conical surfaces. Although desirable from the standpoint of spreading radial loads on the pipe and casing, the shallow tapers increase the radial loads on the pipe and casing, and thus increase the possibility of collapsing the pipe and/or bursting the casing.

[0004] It is also known to reduce radial loading by means of “controlled friction” due to blunt teeth formed on the sides of the slips opposite the teeth for galling the surface over which the slips are slidable.

[0005] It is further known to reduce radial loading by means of slip assemblies of such construction as to exert circumferential loads on the body in order to mimic radial loads.

[0006] According to the primary object of this invention, each of the slips is of such design that it combines desirable features of all three concepts so as to minimize the risk of collapsing the pipe and/or bursting the casing.

[0007] It is a further object to provide a slip assembly of such construction that although the pipe and casing would ordinarily be subjected to radial loading due to the shallow taper of the slips, these loads are minimized by both controlled friction and circumferential loading.

[0008] These and other objects are accomplished, in accordance with an illustrative and preferred embodiment, by apparatus in which a tubular body from which the pipe is suspended is adapted to be lowered into the bore of the casing so as to suspend the pipe therein has longitudinally extending, equally spaced pockets disposed about and concentric with the outer circumference of the body with each pocket having an open face, side walls, and upper and lower end walls. A cone is adapted to be installed within each pocket beneath the upper wall thereof and has an inner cylindrical surface concentric with the body, a downwardly and inwardly extending outer conical surface, and opposite side edges engaging side walls of the pockets. A slip having teeth on its outer side has an inner conical surface concentric with the outer conical surface of each cone for sliding upwardly and vertically with respect thereto. The inner and outer sides of each slip form a relatively small vertical angle with respect to one another, preferably in the range of 2-4 degrees.

[0009] Each side wall of each pocket has a slot adjacent to and extending parallel to the outer conical surface of each cone when in the pocket, and a rib is provided on each lateral side of each slip for fitting closely within a slot as the slip is lowered into the pocket for landing on lower end wall of the pocket so as to retain the cone and slip within the pocket. The slip may be raised over the cone by means of a tie bar having a vertical actuator, for sliding upwardly over the outer conical surface of the cone, to cause the slip teeth to grip the casing and thus suspend the pipe within the casing as the weight of the pipe is slacked off. A tight fit of the side edges of the cone within the side walls of the pocket cause the load to be transmitted to the body in a circumferential direction, and thus as loop loading. The inner side of each slip has relatively blunt teeth for galling the outer side of the adjacent cone when the teeth on the outer side of the slip have engaged the bore of the casing and the weight of the pipe is slacked off onto the casing.

[0010] In the drawings; wherein like reference characters are used throughout to indicate like parts:

[0011]FIG. 1 is a vertical sectional view of the body of the apparatus, as seen along lines 1-1A of FIG. 1A;

[0012]FIG. 1A is an enlarged cross-sectional view of the body, as seen along lines 1A-1A of FIG. 1.

[0013]FIG. 1B is a side view of the body looking in the direction of the pocket;

[0014]FIG. 2 is another vertical section of the body with a cone installed within the pocket thereof as shown along line 2-2 of FIG. 2A;

[0015]FIG. 2A is an enlarged cross-sectional view of FIG. 2, as seen along broken lines 2A-2A of FIG. 2;

[0016]FIG. 3 is another vertical sectional view of the body as soon along line 3-3 of FIG. 3A, upon installation of a slip over the outer side of the cone within the pocket;

[0017]FIG. 3A is another enlarged cross-sectional view of the hanger body as seen along lines 3A-3A of FIG. 3, and showing the ribs on the sides of the slips fitting within the slots in the sides of the pocket so as to hold the cones against the inner faces of the pocket;

[0018]FIG. 4 is a perspective vertical view of the hanger body with the cone and slip removed from the pocket;

[0019]FIG. 5 is a vertical sectional view of the body similar to FIG. 3 but showing the apparatus within a well casing;

[0020]FIG. 5A is a cross-sectional view of the hanger body, slip assembly and casing, as shown along broken lines 5A-5A of FIG. 5; and

[0021]FIG. 6 is a vertical sectional view similar to FIG. 5, and as seen along line 5-5 in FIG. 5, but upon raising of the slip into engagement with the bore of the well casing, whereby the weight of the body and pipe suspended therefrom may be slacked off onto the casing; and

[0022]FIG. 6A-6A is another cross-sectional view of the apparatus, as seen along broken lines 6A-6A of FIG. 6;

[0023]FIG. 6AA is an enlarged detail view of the portion encircled on FIG. 6; and

[0024]FIG. 7 is an enlarged horizontal sectional view of the body, cone, slip and casing illustrating the transmission of forces which result in circumferential or hoop loading of the body as weight is slacked off onto the casing.

[0025] With reference now to the above-described drawings, the apparatus is shown to comprise a tubular body 20 having a bore from which a pipe (not shown) may be suspended within a casing C, as shown in FIGS. 5 and 6. As previously mentioned, this body may be a liner hanger for use in suspending a liner within a well casing. In any case, the body has equally spaced apart pockets 21 formed about its circumference. Each such pocket includes an inner wall 22 concentric to the body, and has upper and lower arcuate walls 23 and 23A which project from the body, as well as sides 24 and 25 which extend radially from the axis of the body.

[0026] More particularly, a slot S is formed in each side wall to extend vertically along a relatively small angle with respect to vertical for extension upwardly and outwardly, with its lower end terminating above the lower wall 24 of the pocket and its upper end vanishing at a point beneath the upper wall 23 of the pocket.

[0027] A cone 30 is adapted to be installed in each slot with its inner cylindrical surface close about the inner wall of the pocket and its outer end being conically shaped for extension upwardly and outwardly. More particularly, outer conical side of the cone forms a relatively small angle with respect to the vertical and thus corresponds to the angle at which the slots extend.

[0028] Upon installation of the cone into the pocket to the position in which its upper end engages the upper wall of the slot, its lower end is disposed above the lower end of the slot. The inner cylindrical sides of the cones fit closely about the faces of the pockets, and the lateral sides thereof fit tight against the sides of the pocket. The outer conical face or side of the cone has a relief 31 formed vertically therein, for a purpose to be described.

[0029] The apparatus further includes slips 40 having conically shaped inner sides conforming to the conical shape of the outside of the cone and a cylindrical outer toothed surface concentric with the axis of the body. More particularly, ribs 42 are provided on each side of the slip for fitting closely within and sliding vertically within the slot on the adjacent side of the pocket until its lower end is over the outer side of the adjacent cone, and its lower end lands on the lower wall of the pocket.

[0030] Since the slots and ribs are adjacent to the outer sides of the cones, this positioning of the slip will cause its inner conical side to fit closely over the outer conical side of the adjacent cone. Thus, mounting of the slip will retain the cone in place within the pocket, but nevertheless free the slip for sliding movement upwardly and outwardly along the outer conical surface of the cone.

[0031] As previously mentioned, and as illustrated in the enlarged detail in FIG. 6AA, blunt teeth BT are formed on the inner side of the cylindrical side of each slip for a purpose previously mentioned and described in more detail to follow.

[0032] As best shown in FIG. 4, the outer side of the upper end of each cone is formed with a vertical groove 35 which is open at its upper end and aligned with a groove 35A in the upper wall of the grooves. More particularly, a tie bar 36 is fixed in any suitable manner to the upper end of each slip for extension upwardly through the grooves and its upper end is adapted for connection with a suitable actuator for raising the slip with respect to the cone.

[0033] With the cone and slips assembled in the pockets thereof the body is lowered into the casing C, as shown in FIG. 5. When the body is initially lowered, the retracted slips are spaced concentrically within the inner circumference of the casing.

[0034] At this time, the tie bars 36 for the slips are lifted, so as to raise the slips over the cones as the ribs on opposite sides of the slips ride within the slots on opposite side walls of the pockets. Thus, due to the concentric conical surfaces on the outer sides of the cones and inner sides of the slips, the slips are caused to move upwardly and outwardly, as their ribs slide within the slots, and thus radially outwardly into biting engagement with the casing, following which the body and weight of the pipe may be suspended therefrom. As previously described and shown in FIG. 6AA, the brunt teeth on the outer sides of the slips will dig into or gall the inner sides of the cones, thereby reducing the radial loads on the body and casing.

[0035] For reasons previously described, the inner and outer sides of the slips form a relatively small angle with respect to one another, preferably in the neighborhood of 2-4 degrees, which spreads the load imposed upon the body and casing over a large area. Although there is a corresponding increase in the magnitude of the radial loading, this is mitigated at least to some extent by the “controlled friction” resulting from the galling of the teeth on the inner sides of the slips into the front sides of the cones.

[0036] Radial loads are further mitigated by their transmission to the body in a circumferential sense, sometimes known as “hoop” loading. Thus, the cones may tend to be flattened, which tendency is promoted by the vertical relief formed in their outer diameters. As previously mentioned, this circumferential loading will further reduce the extent to which the pipe and casing are loaded in a radial sense.

[0037] As indicated diagrammatically in FIG. 7, upon assembly, there is initially a small gap between the opposed back side of the cone and the inner wall 22 of the pocket. As the load is applied through the slip to the cone, the lateral sides of the cone load up onto the sides 24 and 25 of the pocket in the body. This transmits the load through the body in a “hoop” manner instead of tending to collapse the body with a large radial load. As the load increases the gap will decrease until it disappears so that the body will accept some normal load.

[0038] Although the invention has been described in detail, it should be understood that this explanation is for illustration, and that the invention is not limited to these embodiments. Alternate components and installation techniques will be apparent to those skilled in the art in view of this disclosure. Additional modifications are thus contemplated and may be made without departing from the spirit of the invention, which is defined by the claims. 

What is claimed is:
 1. Apparatus for suspending a pipe within a well casing, comprising a body from which the pipe may be suspended and adapted to be lowered into the bore of the casing so as to suspend the pipe therein, longitudinally extending, equally spaced pockets disposed about and concentric with the outer circumference of the body, each pocket having an open face, side walls, and upper and lower end walls, a cone adapted to be installed within each pocket beneath the upper end wall thereof and having an inner cylindrical surface concentric with the body, a downwardly and inwardly extending outer conical surface, and opposite side edges engageable with the side walls of the pocket, a slip having teeth on its outer side and an inner conical surface concentric with the outer conical surface of the cone, the inner and outer sides of each slip forming a relatively small vertical angle with respect to one another, each side wall of each pocket having a slot adjacent to and extending parallel to the outer conical surface of each cone when in the pocket, and a rib on each lateral side of each slip for fitting closely within the slot in the pocket as the slip is lowered into the pocket for landing on its lower end wall so as to retain the cone and slip within the pocket, as the slip slides upwardly and outwardly over the conical surface of the cone as the slip is raised, to cause the slip teeth to grip the casing and thus suspend the pipe within the casing as the weight of the pipe is slacked off, inner side of each slip having relatively blunt teeth for galling the outer side of the adjacent cone after the outer teeth have engaged the bore of the casing and the weight of the pipe is slacked off onto the casing.
 2. As in claim 1, wherein the angle formed between the inner and outer surfaces of each slip is about 2 degrees-4 degrees.
 3. As in claim 1, including a tie bar having its lower end connectible to the upper end of each slip and adapted to be raised by an actuator for raising the slip.
 4. As in any one of claims 1 to 3, wherein the body is a hanger from which a liner is suspended. 